Patent EP 214880 describes a method for producing polyvinylidene fluoride copolymers by grafting a monomer onto the polyvinylidene fluoride by means of ionizing radiation and comprising the following successive steps:                a) a polyvinylidene fluoride powder or film is immersed in a solution of a monomer chosen from the group comprising acrylamide, styrene, methylstyrene, allyl glycidyl ether, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate, dimethylaminopropyl acrylate and dimethylaminopropyl methacrylate, diethylaminoethyl acrylate and diethylaminoethyl methacrylate, diethylaminopropyl acrylate and diethylaminopropyl methacrylate, dimethylaminopropyl methacrylamide, N-vinylpyrrolidone, N-vinylcaprolactone, acyloxystyrenes and hydroxystyrenes, vinylsulfonic acid and its derivatives, acrylic acid and methacrylic acid, in order to impregnate the polyvinylidene fluoride powder or film with said monomer;        b) the impregnated powder or film is irradiated by means of ionizing radiation in the absence of oxygen; and        c) the grafted copolymer obtained is then subjected to a chemical reaction in order to give it an ionic character when the grafted monomer is not ionic in character.        
Patent application WO 00/17889 describes electrical cable jackets comprising, in succession, a layer consisting of an ethylene/alkylacrylate/maleic anhydride terpolymer and a layer of a VDF/HFP fluorocopolymer. To improve the adhesion of these layers, they are both subjected to ionizing radiation.
U.S. Pat. No. 5,576,106 describes a method for grafting an unsaturated functional monomer onto the surface of fluoropolymer powder. Powdered maleic anhydride and the fluoropolymer are blended together and then placed in a polyethylene bag and, after the air contained in the bag has been expelled, the bag containing the powder blend is subjected to irradiation of between 3 and 6 Mrad. In one variant, maleic anhydride is dissolved in acetone, the solution is then blended with the fluoropolymer powder, and then the acetone is evaporated. Next, an irradiation step is carried out as above. The fluoropolymer modified by radiation grafting is then used in multilayer structures. In all the examples, only fluoroelastomers are used. The peel forces between a layer of fluoropolymer modified by irradiation grafting according to these examples of the prior art and another material are insufficient for many applications, in particular in structures comprising polyolefins.
U.S. Pat. No. 5,409,997 describes a composition based on an ethylene/tetrafluoroethylene/termonomer terpolymer crosslinked using a difunctional compound stable up to 200° C. and above, and grafted by irradiation. The preferred difunctional compounds are metal di(meth)acrylates, such as zinc diacrylate or zinc dimethacrylate.